Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses

Phosphorus (P) is an essential and often limiting element that could play a crucial role in terrestrial ecosystem responses to climate warming. However, it has yet remained unclear how different P cycling processes are affected by warming. Here we investigate the response of soil P pools and P cycling processes in a mountain forest after 14 years of soil warming (+4 °C). Long-term warming decreased soil total P pools, likely due to higher outputs of P from soils by increasing net plant P uptake and downward transportation of colloidal and particulate P. Warming increased the sorption strength to more recalcitrant soil P fractions (absorbed to iron oxyhydroxides and clays), thereby further reducing bioavailable P in soil solution. As a response, soil microbes enhanced the production of acid phosphatase, though this was not sufficient to avoid decreases of soil bioavailable P and microbial biomass P (and biotic phosphate immobilization). This study therefore highlights how long-term soil warming triggers changes in biotic and abiotic soil P pools and processes, which can potentially aggravate the P constraints of the trees and soil microbes and thereby negatively affect the C sequestration potential of these forests.

I found the results very interesting and think they will provide a valuable contribution to the literature. While the experiment and data appear robust, I think a substantial revision is needed for the paper to be worthy of publication. In its current format the manuscript fails to provide sufficient background to provide a rationale for the presented hypotheses, or to place the results in the context of the wider literature. In places the paper reads more like a summary/synthesis of this specific experiment (drawing on other papers currently in review elsewhere) rather than reporting a new finding in the context of the wider literature.
For example, the final conclusions paragraph is a summary of the results from this experiment and no effort is made to put the results in the context of the literature, or to present the wider relevance and context of the findings -the paragraph includes no citations of other work.
I am also concerned about how the results here are framed as representing a comparison of 'topsoil' vs. 'subsoil', based on a very marginal depth difference of 0-10cm vs 10-20cm. Similarly, for the 'seasonal' patterns there was no sampling during winter.
The main findings reported (Table 1, Figure 1-2) are indeed interesting. However, it must be emphasised that all the reported results are based on correlations only. Therefore, greater caution is needed to describe these as correlations rather than causal relationships when inferring mechanisms in the discussion.

Specific comments:
Title: I'm not sure 'impairs' is an appropriate description of the results. Impairs means to diminish in function, which I don't think is reflected here in terms of P cycling. The manuscript shows interesting changes in P cycling, with immobilisation and increased enzyme investment, but I don't think this can be summarised as being an impaired.

REVIEWER COMMENTS
Reviewer #1 (Remarks to the Author): The authors use a 14-year soil warming experiment in a mountain forest in Austria, to investigate soil P pools and soil P cycling in response to warming. The authors demonstrate decreased P mobilisation and increased P immobilisation, despite an increase in activity of phosphatase enzymes. The authors then present a framework of mechanisms on how P immobilisation is correlated to the abundance of Fe-Al oxyhydroxides; and how in turn this may be related to root production and microbial P dynamics (biomass immobilisation and phosphatase activity; although the latter two are from different manuscripts published elsewhere and only summarised here). I found the results very interesting and think they will provide a valuable contribution to the literature. While the experiment and data appear robust, I think a substantial revision is needed for the paper to be worthy of publication. In its current format the manuscript fails to provide sufficient background to provide a rationale for the presented hypotheses, or to place the results in the context of the wider literature. In places the paper reads more like a summary/synthesis of this specific experiment (drawing on other papers currently in review elsewhere) rather than reporting a new finding in the context of the wider literature.
For example, the final conclusions paragraph is a summary of the results from this experiment and no effort is made to put the results in the context of the literature, or to present the wider relevance and context of the findings -the paragraph includes no citations of other work.
I am also concerned about how the results here are framed as representing a comparison of 'topsoil' vs. 'subsoil', based on a very marginal depth difference of 0-10cm vs 10-20cm. Similarly, for the 'seasonal' patterns there was no sampling during winter.
The main findings reported (Table 1, Figure 1-2) are indeed interesting. However, it must be emphasised that all the reported results are based on correlations only. Therefore, greater caution is needed to describe these as correlations rather than causal relationships when inferring mechanisms in the discussion.

Specific comments:
Title: I'm not sure 'impairs' is an appropriate description of the results. Impairs means to diminish in function, which I don't think is reflected here in terms of P cycling. The manuscript shows interesting changes in P cycling, with immobilisation and increased enzyme investment, but I don't think this can be summarised as being an impaired.
Line 34: 'By the end' instead of 'Until' Lines 48-49: Sentence doesn't make sense to me -Please check language here ('did either promote or have no effects').
Lines 51-53: Would be improved here by describing in more detail the studies have looked at P dynamics in warmed soils, and being more explicit about what is novel here. For example, recent paper on P mobilisation in warmed soils by Zhou et al: https://doi.org/10.1111/gcb.15914.
Lines 59-60: The rationale behind studying changes across soil depth is very insubstantial. If soil depth is an important part of this study then more detail is needed on why responses in deep soils by differ, providing rationale for hypotheses on response differences across soil depths.
Lines 60-61: As above for soil depth, scarce information here on why seasonality is important in the context of this study, to provide a rationale for any hypotheses on seasonal dynamics. Suggest specifying what properties change seasonally and explicitly framing hypotheses on those seasonal changes (e.g. temperature/moisture -how change seasonally, how will this affect P dynamics under warming?).
Lines 63-64: Related to the above here it is stated that the overall objective of this study is to investigate how warming affects soil P… 'across soil depths and seasons'. Given this overall objective, please include more detail in the introduction on why depth/season is important (both for this study site -and in the context of other study sites).
Line 74: The soil depths for this study are 0-10cm and 10-20cm. What soil horizons do these represent? I would have thought they are both representative of O or O-A horizons. Please include this information for these soils. Are soil properties across this 10cm depth differences sufficiently different to warrant using this as an experimental comparison? If there is a large difference, then it should be explained here so the reader understands that 0-10 cm vs. 10-20cm represents a valid comparison of different soil environments.
Line 74: The seasonal comparison here is May, August, October; and includes no observation during the winter. I think some justification is needed to explain why these three months were selected, and when discussing seasonal dynamics it should be mentioned that no observations were made during the coldest months.
Line 80: Related to above comment, here the '10-20cm' treatment is described as 'subsoil'. I would suggest subsoil would come from the B horizon (usually much deeper, at least >30cm), and have significantly less organic matter than the top soil. Please present properties on these two soil horizon treatments, to provide a justification for their use as a treatment comparison.
Line 83: Please describe how and why warming 'facilitates plant P uptake from soil to reduce soil P pools'?
Lines 87-91: Suggest review and re-write this text with greater focus. In its present form I find this text confusing and appears as a straw-man argument. Initially it is suggested that the results imply higher P demand and greater P uptake; but in the following sentence it is stated that root P contents did not hange. Therefore, if root P contents did not change, isn't this evidence against greater P uptake? Lines 92-106: A common problem in this manuscript is the lack of evidence drawn from the literature, to place the reported results in a wider context. This paragraph is one example of that. Many conjectures are made (e.g. lines 100-103) with no supporting literature cited.
Lines 123-127: Here and elsewhere, greater caution is needed when inferring mechanisms based on correlations. (e.g. here a direct mechanism is inferred based on a correlation 'increased Fe oxyhydroxide contents in warmed soils contributed to a greater abiotic P immobilisation strength').
Lines 140-150: This text about the geology of the study sites appears out of place here, perhaps this could be better placed in the methods or site description.
Lines 150-160: This text needs a significant re-write to remove speculation and to base the discussion on the results and grounded in the wider literature. At present the text includes no references to other studies, but is full of speculation without any support. e.g. 'the trend towards'.. 'might have contributed, but we cannot attributed this to a warming effect'. 'It seems rather unlikely that warming affected soil texture, but it may not be totally ruled out…' It's fine to have some speculation, but it needs to be firmly grounded in a hypothesis based on evidence if not evidence from this study, then evidence from elsewhere). : This paragraph appears to summarise results from another study currently in review elsewhere. Overall, as I read this paper I'm confused as to whether it's a results paper or a review/summary paper (either are fine -but I would suggest the authors consider which to frame this as during revision).
Lines 205-222: The conclusions paragraph is another example of the lack of depth here. The paragraph reads as a list of results and includes no references to other work.

GENERAL COMMENTS:
This paper addresses an important topic in soil science: contributes to a better understanding of soil P biotic and abiotic cycling under main drivers of global change. In particular the work tries to shed some light on the effect of warming over abiotic processes (weathering, P sorption), processes that are very often overlooked on soil warming experiments (commonly centered in understanding biological responses).
A noteworthy result of this manuscript is the relation between the decrease of total soil P pools under warming with an increased sorption strength for inorganic P to iron oxyhydroxides and clay. This work proves that abiotic processes are important as biotic ones as drivers of important changes in nutrient cycling under global change. This work is of significance to the field and related fields. The processes described are not new (soil P pathways organic and inorganic cycling). However, the novelty of this work consists in applying a very complete set of measurements to a mid-term (14 years) warming experiment providing a complete in-depth study of soil P cycle.
This manuscript addresses topics of main-line interest to Nature Communications, it is well-written and thoroughly referenced. The title is appropriate, the abstract conveys the main points, and the overall conclusions are of wide interest. However, I have concerns on some points of the discussion and I miss a better graphical (Figures) support. If the points addressed bellow are improved enough I would recommend its publication by the requested journal.
I would ask the authors why they refer to dissolved inorganic/organic P instead of the commonly used "available P" or P-Olsen. DOP and DIP terms result confusing as they are mainly terms applied to water studies.
The authors affirm on page 4 (line 69) that inorganic P sorption decreases at higher temperatures and include a reference that support this statement. However, most literature demonstrate that sorption processes are higher at higher temperatures (when these are close to ambient temperatures 5-25°C).
From my point of view, it is missing in the text a better description of the soil type (classification, mineralogy, horizons depth) on the main text to provide elements for a more comprehensive discussion. At certain part of the discussion the authors refer to a high spatial heterogeneity in texture of the sampled soils and the presence of loamy moraine sediments as subsoils. This information would provide a better understanding of the site and soil processes if introduced before together with more accurate descriptions.
The authors argue possible biotic pathways to explain the decrease of total P pools. This includes a higher uptake by plants explained by an increase in fine root production. What are the implications and limitations of the experimental design to evaluate plant response to warming? In contrast to what happens with current climate change, in this case the soil is warmed but not the aboveground which restricts or unbalances plant response to belowground adaptations.
Higher Fe hydroxide content after warming treatments is attributed to faster weathering processes. This affirmation is surprising as a result of a 14-years warming. This is because weathering intensity directly relates to temperature, CO2 concentration and precipitation but it is generally attributed to longer time scales (millennial). There aren't many published studies considering the role of weathering changes at decadal time scales. I would appreciate that the authors develop more this idea including more references. At the moment the effects of the climate-change induced changes in weathering are not well studied and understood.
Apart from clay mineralogy, what are the primary minerals? Which is the mineral phase attributed to the crystalline Iron? When compared with the total mineralogy (not only clays), is it possible to estimate the % of amorphous and crystalline Iron?
Figures can be improved. Figure 1 can incorporate the complete variable name on PCA loadings. It is recommendable to use color blind friendly palettes (easy available in R). More elements for discussion could be derived from Figure 1, as the meanings or interpretation for PC1 or PC2.
On Figure 2, samples could be distinguished among treatments. I recommend the authors to include a third and final Figure with a schematic representation of the main processes described. I would consider this third Figure essential to achieve publication in the requested journal.
I encourage the authors to reinforce in a clearer way what is new from their contribution, and to remark its importance in relation to the global understanding of soil carbon and nutrient cycling.

SPECIFIC COMMENTS
Pag 3 line 35: current warming is already above 1°C above pre-industrial levels Pag 5 line 100: Soil water loss is expected to be higher at the top soil than at the subsoil, is it like this? Can this relate to changes on DOP and DIP between different depths through a higher reduction of diffusion capacity on the top soil? Pag 7 line 139: First time mention to elements of soil description, better mention them earlier.
Pag 7 line 144: better "moderate" instead of high Pi sorption capacity when referring to kaolinite. It has lower sorption capacity than 2:1 clay. The same for line 175 when is mentioned "strong P-sorbing" kaolinite.
We are grateful to the reviewers' comments, which helped us improve the manuscript. We addressed most comment individually and several highly connected comments together. The responses are in green for clarity, and corresponding changes in the manuscript are highlighted in yellow in the revised manuscript. Besides, we carefully followed the guide to formatting articles for Nature Communications, and made minor changes (highlighted in orange) in the revised manuscript and in the revised display files.

REVIEWER COMMENTS
Reviewer #1 (Remarks to the Author): The authors use a 14-year soil warming experiment in a mountain forest in Austria, to investigate soil P pools and soil P cycling in response to warming. The authors demonstrate decreased P mobilisation and increased P immobilisation, despite an increase in activity of phosphatase enzymes. The authors then present a framework of mechanisms on how P immobilisation is correlated to the abundance of Fe-Al oxyhydroxides; and how in turn this may be related to root production and microbial P dynamics (biomass immobilisation and phosphatase activity; although the latter two are from different manuscripts published elsewhere and only summarised here). I found the results very interesting and think they will provide a valuable contribution to the literature. While the experiment and data appear robust, I think a substantial revision is needed for the paper to be worthy of publication. In its current format the manuscript fails to provide sufficient background to provide a rationale for the presented hypotheses, or to place the results in the context of the wider literature. In places the paper reads more like a summary/synthesis of this specific experiment (drawing on other papers currently in review elsewhere) rather than reporting a new finding in the context of the wider literature.
For example, the final conclusions paragraph is a summary of the results from this experiment and no effort is made to put the results in the context of the literature, or to present the wider relevance and context of the findings -the paragraph includes no citations of other work.

1-1.Author response:
We thank the reviewer for the positive comments and feedback. We integrated all the comments and suggestions in the revised manuscript. For the detailed responses, please see below.
I am also concerned about how the results here are framed as representing a comparison of 'topsoil' vs. 'subsoil', based on a very marginal depth difference of 0-10cm vs 10-20cm. Similarly, for the 'seasonal' patterns there was no sampling during winter.

1-2.Author response:
We added a new table (Table 1, see the revised Display document) showing the comparison of soil properties from 0-10 cm and 10-20 cm soil depth in the warming and control treatments. According to this table, the readers can see the substantial difference between these two soil layers, e.g. the soil organic carbon content is almost double at 0-10 cm compared to 10-20 cm soil depth. Besides, we replaced "top-and subsoil" with "0-10 and 10-20 cm" to be more accurate. Moreover, these soils are very shallow, being Chromic Cambisols and Rendzic Leptosols, where at most spots in this forest one arrives at the C horizon at only 20-25 cm depth.
Regarding the exclusion of winter sampling, the reason is that we only heat up the warming plots during the snow-free seasons, i.e. during winter time warmed plots are at ambient temperature. There is snow cover (up to 1 m) at our site during winter months. Snow cover can act as thermal insulation layer, which keeps the soil temperatures of control plots always above 0 °C. As the soil temperatures in warming plots are based on the soil temperatures of their adjacent control plots plus 4 °C, these higher soil temperatures would melt the snow cover in the warming treatment, which dramatically changes environmental conditions between warming and control treatments during winter. Given an eventual overload of the warming capacity by the heating cables, this could even lead to a cooling of warmed plots during winter time, which we did not intend to study here, and to strong changes in the soil hydrological properties during spring, when no snow can melt in warmed plots to sustain high soil water contents. Therefore, we only heated up the warming plots during the snow-free seasons, and thus we did not sample soils in winter months, where soils are not warmed. We now added specification in the Methods section (see below) and in Introduction section (Line 75) to clarify the warming treatment in the main text.

Manuscript:
The heating system is only running during the snow-free season (April to November) to avoid substantial differences in environmental conditions between warming and control treatments, due to warming-induced snow melting and adverse effects on soil hydrology (Lines 258-261).
The main findings reported (Table 1, Figure 1-2) are indeed interesting. However, it must be emphasised that all the reported results are based on correlations only. Therefore, greater caution is needed to describe these as correlations rather than causal relationships when inferring mechanisms in the discussion.

1-3.Author response:
We re-structured and rephrased the explanations to avoid over-interpreting the correlation results and added new citations to support the interpretations. Though the results are based on LMEs and on correlations, which is correct, the mechanisms underlying the observed changes have been published, e.g. on clay and Fe/Al oxide effects on Pi sorption, and are also hard to manipulate in the field.

Manuscript:
1-3-1. According to the principal component analysis (PCA), dithionite-extractable Fe was closely and positively associated with abiotic P immobilization (Fig. 2). Besides, dithionite-extractable Fe and crystalline Fe oxides were positively correlated with abiotic P immobilization and negatively correlated with (log-transformed) Olsen P (Fig. 3a- . In this study, sand content was significantly lower in warmed soil, whereas clay content was 11% higher than in control soil (though not significant). According to the results of PCA, abiotic Pi immobilization was negatively associated with soil sand content, while it co-varied positively with soil clay content (Fig. 2). Soils with higher sand content commonly exert lower P sorption capacity as the dominant quartz particles in the sand size fraction only have weak bonding affinity to P, whereas soils with high clay content often exhibit higher P sorption capacity, because of a large specific surface area and abundant bonding sites to P (Spohn 2020; Martin et al., 2018; Jalali and Jalali, 2016). Thereby, the lower sand content in combination with a higher clay content (but unaltered clay mineralogy) in warmed soil can be another reason for the intensified abiotic Pi immobilization (Lines 146-158).

Newly added references:
Herndon Specific comments: Title: I'm not sure 'impairs' is an appropriate description of the results. Impairs means to diminish in function, which I don't think is reflected here in terms of P cycling. The manuscript shows interesting changes in P cycling, with immobilisation and increased enzyme investment, but I don't think this can be summarised as being an impaired.
1-4.Author response: We meant to express that long-term soil warming decreased (impaired) microbial P utilization, and greater production of phosphatase did not compensate for this, as microbial biomass P decreased. Now we changed the title to "Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses" (Lines 1-2).
Lines 48-49: Sentence doesn't make sense to me -Please check language here ('did either promote or have no effects').
Lines 51-53: Would be improved here by describing in more detail the studies have looked at P dynamics in warmed soils, and being more explicit about what is novel here. For example, recent paper on P mobilisation in warmed soils by Zhou et al: https://doi.org/10.1111/gcb.15914. 1-7.Author response: We thank the reviewer for this suggestion. We now added multiple references that investigate the warming effects on abiotic P processes, and more explicitly describe the novelty of this study.

Manuscript:
So far, a very limited number of warming studies have investigated soil abiotic P processes, and most of these studies assessed the warming effects on abiotic P processes indirectly, via comparing the changes of different P pools between warming and control treatments ( , which allows to quantify the process rates of gross and net (biotic and abiotic) P mobilization and immobilization, and thereby directly examined how specific soil P transformation processes responded to long-term soil warming. Moreover, soil P processes and P pools are highly connected and interacting ( Lines 59-60: The rationale behind studying changes across soil depth is very insubstantial. If soil depth is an important part of this study then more detail is needed on why responses in deep soils by differ, providing rationale for hypotheses on response differences across soil depths. Lines 60-61: As above for soil depth, scarce information here on why seasonality is important in the context of this study, to provide a rationale for any hypotheses on seasonal dynamics. Suggest specifying what properties change seasonally and explicitly framing hypotheses on those seasonal changes (e.g. temperature/moisture -how change seasonally, how will this affect P dynamics under warming?).
Lines 63-64: Related to the above here it is stated that the overall objective of this study is to investigate how warming affects soil P… 'across soil depths and seasons'. Given this overall objective, please include more detail in the introduction on why depth/season is important (both for this study site -and in the context of other study sites).
1-8.Author response: We wrote a separate paragraph to explain why soil depth and seasonality are important in the context of this study. There are strong changes in soil physicochemistry and microbiology with soil depth, having considerable impacts on abiotic and biotic processes, including those related to soil P cycling, but those have rarely been studied in terms of global change effects. Moreover, several studies showed that warming effects can strongly change across seasons (see citations). However, since this study mainly focused on soil warming effects and most of the measured properties, pools, and processes had no interactions between warming, soil depth, and/or season, we prefer to keep the explanation brief.

Manuscript:
The warming response of soil P pools and soil P processes could be modulated by soil depth, since physicochemical soil properties, microbiological properties, and nutrient conditions strongly vary with soil depth ( Line 74: The soil depths for this study are 0-10cm and 10-20cm. What soil horizons do these represent? I would have thought they are both representative of O or O-A horizons. Please include this information for these soils. Are soil properties across this 10cm depth differences sufficiently different to warrant using this as an experimental comparison? If there is a large difference, then it should be explained here so the reader understands that 0-10 cm vs. 10-20cm represents a valid comparison of different soil environments.

1-9.Author response:
We added Table 1 (see in the revised Display document), which shows the comparison of soil properties at 0-10 cm and 10-20 cm soil depth in the warming and control treatments. As you can see, many of these soil properties significantly differ at 0-10 cm and 10-20 cm depth, most of them decreasing. Besides, since the soil has developed from dolomite bedrock, it is in general very shallow, being Chromic Cambisols and Rendzic Leptosols, where at most spots in this forest one arrives at the C horizon at only 20-25 cm depth. We now replaced "topsoil" and "subsoil" with "0-10 cm" and "10-20 cm" throughout the manuscript to make the manuscript clearer, the previous topsoil referring to the A horizon, and the previous subsoil constituting the AC horizon.
Line 74: The seasonal comparison here is May, August, October; and includes no observation during the winter. I think some justification is needed to explain why these three months were selected, and when discussing seasonal dynamics it should be mentioned that no observations were made during the coldest months.

1-10. Author response:
As mentioned in 1-2, we added more explanation in the site description section in Methods (Lines 258-261), and also mentioned that no observations were made during the snow-free seasons in the Introduction (Line 75).
Line 80: Related to above comment, here the '10-20cm' treatment is described as 'subsoil'. I would suggest subsoil would come from the B horizon (usually much deeper, at least >30cm), and have significantly less organic matter than the top soil. Please present properties on these two soil horizon treatments, to provide a justification for their use as a treatment comparison.

1-11. Author response:
Thanks for the suggestion. As addressed in 1-2 and 1-9, we added a new table (Table 1) to provide more information on the differences of soil properties between these two soil depths. We haven't measured soil organic matter content in our soils, but the soil organic carbon is almost double at 0-10 cm compared to 10-20 cm soil depth, indicating substantial differences between 0-10 cm and 10-20 cm soil depth at our site. Moreover, 0-10 cm represents the A horizon and 10-20 cm the AC horizons at this site. Almost all other physicochemical parameters also changed across these depth increments.
Line 83: Please describe how and why warming 'facilitates plant P uptake from soil to reduce soil P pools'?

1-12. Author response:
We extended the explanation and added two meta-analysis papers to make it more understandable and convincing.

Manuscript:
Elevated soil temperatures, in general, facilitate plant growth, while warming had no effects on plant C:P ratios in temperate forest ecosystems (Lu et al., 2013; Yue et al., 2017). This indicates a higher plant P uptake, which removes P from soil to plant, in turn reducing total soil P pools (Lines 93-95).
Lines 87-91: Suggest review and re-write this text with greater focus. In its present form I find this text confusing and appears as a straw-man argument. Initially it is suggested that the results imply higher P demand and greater P uptake; but in the following sentence it is stated that root P contents did not hange. Therefore, if root P contents did not change, isn't this evidence against greater P uptake?
1-13. Author response: We modified the description to make it clearer.

Manuscript:
Elevated soil temperatures, in general, facilitate plant growth while warming had no effects on plant C:P ratios in temperate forest ecosystems (Lu et al., 2013; Yue et al., 2017). This indicates a higher plant P uptake, which removes P from soil to plant, in turn reducing total soil P pools. Kengdo et al., who studied fine root production, morphology, and element contents at the same site, reported an 128% increase in fine root production, 17% increase in fine root biomass, and unchanged fine root P content in the warming treatment compared to the control treatment. These results imply a higher P demand of the trees for fine root production and potentially greater root P uptake and P immobilization in long-lived plant biomass, ultimately reducing soil total P in warmed soils ( . However, this substantially higher fine root production compared to moderate biomass increase indicate a faster fine root turnover, which suggests a reflux of P from decomposing root necromass into the soil, attenuating the soil P loss pathway from plant uptake (Lines 93-105).

Newly added references:
Kwatcho Lines 92-106: A common problem in this manuscript is the lack of evidence drawn from the literature, to place the reported results in a wider context. This paragraph is one example of that. Many conjectures are made (e.g. lines 100-103) with no supporting literature cited.

1-14. Author response:
We now added several citations to support the explanation.

Manuscript:
Moreover, soil P can be lost from terrestrial systems as dissolved P and P that is bound to soil particles (particulate P), via leaching and erosion processes ( , but this was not confirmed by soil solution chemistry (dissolved P in soil water was always below the detection limit; data not shown). Soil water P concentrations are generally low, but we found a decrease in 0.5 M NaHCO3 extractable dissolved organic P (Olsen Po) at 0-10 cm soil depth in the warming treatment, when calculating the ratio of Olsen Po at 0-10 cm soil depth divided by Olsen Po in 10-20 cm (decrease from 1.16 in controls to 0.99 in warmed soils), indicating a higher net downward transport (leaching) of Olsen Po in warmed soils. Besides, even at high mean annual precipitation in old-growth forests, soil erosion and related particulate P losses likely do not play a large role, due to the high canopy and litter cover, effectively curtailing erosion in dense forests (Bavor 1956). Overall, net losses of total P from the soils were mainly due to downward leaching of Olsen Po to lower soil layers, as the increased root P uptake was largely compensated by enhanced reflux of root P through increased root turnover (Lines 106-121).

Newly added references:
Alewell Lines 123-127: Here and elsewhere, greater caution is needed when inferring mechanisms based on correlations. (e.g. here a direct mechanism is inferred based on a correlation 'increased Fe oxyhydroxide contents in warmed soils contributed to a greater abiotic P immobilisation strength').
Lines 140-150: This text about the geology of the study sites appears out of place here, perhaps this could be better placed in the methods or site description.

1-16. Author response:
Thanks for the suggestion! We now moved this text to the site description in the methods section (Lines 238-249).
Lines 150-160: This text needs a significant re-write to remove speculation and to base the discussion on the results and grounded in the wider literature. At present the text includes no references to other studies, but is full of speculation without any support. e.g. 'the trend towards'.. 'might have contributed, but we cannot attributed this to a warming effect'. 'It seems rather unlikely that warming affected soil texture, but it may not be totally ruled out…' It's fine to have some speculation, but it needs to be firmly grounded in a hypothesis based on evidence if not evidence from this study, then evidence from elsewhere).

1-17. Author response:
We modified this paragraph by minimizing speculations and adding multiple citations to make the discussion sounder.

Manuscript:
Soil texture and clay mineralogy are also relevant for abiotic Pi immobilization; especially clay minerals with a high specific surface area can form stable chemical bonds with P via calcium (Ca 2+ ) and magnesium (Mg 2+ ) bridges (Bünemann et al., 2010; Spohn 2020). In this study, sand content was significantly lower in warmed soil, whereas clay content was 11% higher than in control soil (though not significant). According to the results of PCA, abiotic Pi immobilization was negatively associated with soil sand content, while it co-varied positively with soil clay content (Fig. 2). Soils with higher sand content commonly exert lower P sorption capacity as the dominant quartz particles in the sand size fraction only have weak bonding affinity to P, whereas soils with high clay content often exhibit higher P sorption capacity, because of a large specific surface area and abundant bonding sites to P (Spohn 2020; Martin et al., 2018; Jalali and Jalali, 2016). Thereby, the lower sand content in combination with a higher clay content (but unaltered clay mineralogy) in warmed soil can be another reason for the intensified abiotic Pi immobilization.
So far, short-term (decadal) warming effects on soil metal oxides, soil texture and clay mineralogy have rarely been studied. Lines [177][178][179][180][181][182][183][184][185][186][187][188][189][190][191]: This paragraph appears to summarise results from another study currently in review elsewhere. Overall, as I read this paper I'm confused as to whether it's a results paper or a review/summary paper (either are fine -but I would suggest the authors consider which to frame this as during revision).

1-18. Author response:
This manuscript is a result paper as one might see from the Methods section. We drew on this parallel study on microbial C-N-P limitation here to provide more evidence of that long-term warming-induced microbial P limitation. We now shortened the summary of their results.

Manuscript:
Soil microbes compete with abiotic cycling processes for available P in soil solution ( Fig. 1; Reed et al., 2015; Olander & Vitousek, 2004). Reduced soil total P after long-term warming likely intensified this competition between abiotic immobilization and microbial processes in warmed soils. Moreover, enhanced abiotic Pi immobilization in the warming treatment depleted available P for soil microbes. In a C-N-P substrate addition experiment, Shi et al. (Global Change Biology, in revision) measured the stimulation of microbial growth in response to substrate amendments as an indicator of microbial element limitation in the same soils in August 2019. They found a strong stimulation of microbial growth in the combined C-P amendment than in the C-only addition in the warming treatment. In contrast, there was no difference in microbial growth stimulation between the combined C-P amendment and the C-only amendment in control soils. These results confirmed that, after 14 years of forest soil warming, soil microbes have increasingly become constrained by P in the warming treatment (Lines 182-194).
Lines 205-222: The conclusions paragraph is another example of the lack of depth here. The paragraph reads as a list of results and includes no references to other work.

1-19. Author response:
We shortened the results and modified the conclusion. In a conclusion, however, it is not usual to cite (multiple) references, but rather to summarize the results and give an outlook on the implications of the work to be published. We therefore remarked the importance of this study: 1) providing novel data of long-term warming effects on soil P process rates; 2) long-term warming can drive temperate forest soils to become P limited; 3) which can further affect soil C and N cycling.

Manuscript:
In conclusion, this study contributes novel data on warming effects on soil P processes, providing a more comprehensive understanding of climate change effects on the soil P cycle (Fig. 1). Our results suggest that long-term warming strongly reduced soil available P, which resulted from substantial losses of TP (via leaching and plant P uptake) and enhanced Pi sorption (onto Fe oxide and clay minerals), and can turn temperate forest soils to P limited (Du et al., 2020). As a response, soil microbes changed their allocation of C (energy) and nutrients to acquire P This paper addresses an important topic in soil science: contributes to a better understanding of soil P biotic and abiotic cycling under main drivers of global change. In particular the work tries to shed some light on the effect of warming over abiotic processes (weathering, P sorption), processes that are very often overlooked on soil warming experiments (commonly centered in understanding biological responses).
A noteworthy result of this manuscript is the relation between the decrease of total soil P pools under warming with an increased sorption strength for inorganic P to iron oxyhydroxides and clay. This work proves that abiotic processes are important as biotic ones as drivers of important changes in nutrient cycling under global change. This work is of significance to the field and related fields. The processes described are not new (soil P pathways organic and inorganic cycling). However, the novelty of this work consists in applying a very complete set of measurements to a mid-term (14 years) warming experiment providing a complete in-depth study of soil P cycle.
This manuscript addresses topics of main-line interest to Nature Communications, it is well-written and thoroughly referenced. The title is appropriate, the abstract conveys the main points, and the overall conclusions are of wide interest. However, I have concerns on some points of the discussion and I miss a better graphical (Figures) support. If the points addressed bellow are improved enough I would recommend its publication by the requested journal.
I would ask the authors why they refer to dissolved inorganic/organic P instead of the commonly used "available P" or P-Olsen. DOP and DIP terms result confusing as they are mainly terms applied to water studies.

2-1.Author response:
Thanks for the suggestion. We replaced "dissolved inorganic/organic P" with "Olsen Pi/Po" throughout the manuscript.
The authors affirm on page 4 (line 69) that inorganic P sorption decreases at higher temperatures and include a reference that support this statement. However, most literature demonstrate that sorption processes are higher at higher temperatures (when these are close to ambient temperatures 5-25°C).

2-2.Author response:
We apologize for the misuse of these references. In general, sorption is an exothermic process. Besides, increased temperature can decrease the attractive force between adsorbed molecules and the sorption surface. Thus, higher temperature should weaken the sorption process. We now updated the references.
From my point of view, it is missing in the text a better description of the soil type (classification, mineralogy, horizons depth) on the main text to provide elements for a more comprehensive discussion. At certain part of the discussion the authors refer to a high spatial heterogeneity in texture of the sampled soils and the presence of loamy moraine sediments as subsoils. This information would provide a better understanding of the site and soil processes if introduced before together with more accurate descriptions.

2-3.Author response:
Thanks for the suggestion! We added a separate paragraph describing the soil information in the site description section in the Methods.

Manuscript:
The bedrock is formed of dolomite. The soils are characterized as Chromic Cambisols and Rendzic Leptosols (based on the World Reference Base for Soil Resources), with high carbonate content and near-neutral pH. The 0-10 cm soil increment largely represents the A horizon, and the depth increment of 10-20 cm is an AC horizon. The depth increment below 20-25 cm is constituted by the C horizon, with more than 80% represented by coarse dolomite rock. Moreover, soils exhibit a high spatial heterogeneity in texture (primarily determined by micro-topography) and resemble a smallscale mosaic of autochthonous young A/C profile soils. The soils contain older loamy moraine sediments, which were deposited by glaciers during the last ice age, as subsoils. Besides, in the clay fraction, our site was dominated by kaolinites (~60%), followed by chlorites associated with a mixed layered clay (~30%), and illites (~10%). This high contents of kaolinite in the clay fraction, a very stable clay mineral with high to moderate Pi sorption capacity, clearly could not have formed during the last deglaciation phase (10,000 to 15,000 years). That indicates inputs via aeolian deposition from older nearby soil formations and inputs from the Central Alps. Accordingly, soil texture showed high spatial variability within the different control and warming plots (Lines 233-249).
The authors argue possible biotic pathways to explain the decrease of total P pools. This includes a higher uptake by plants explained by an increase in fine root production. What are the implications and limitations of the experimental design to evaluate plant response to warming? In contrast to what happens with current climate change, in this case the soil is warmed but not the aboveground which restricts or unbalances plant response to belowground adaptations.

2-4.Author response:
We agree with the reviewer that the results from soil warming experiment and soil+canopy warming experiment may differ, however, due to technical and financial constraints we are not aware of any warming experiment of a full mature temperate, boreal or tropical forest (above+belowground) with an average canopy height of >25 m. We would have ideas to do so, but this would also incur very strong unwanted micrometeorological effects and cost multi-millions of Euros to setup.
With canopy warming, it most likely can increase gross plant P uptake from soil due to facilitated photosynthesis, but can also increase litter P inputs to soils. However, due to the relocation of foliar P from old leaves to other tissues, especially in P restricted environments, soil+canopy warming experiment may have higher net plant P uptake than soil warming experiment. We are fully aware of that we only warmed limited part of trees in each plot. This was why we toned down the interpretation of plant P uptake pathway in our manuscript (Lines 102-105 and Lines 118-121).
Higher Fe hydroxide content after warming treatments is attributed to faster weathering processes. This affirmation is surprising as a result of a 14-years warming. This is because weathering intensity directly relates to temperature, CO2 concentration and precipitation but it is generally attributed to longer time scales (millennial). There aren't many published studies considering the role of weathering changes at decadal time scales. I would appreciate that the authors develop more this idea including more references. At the moment the effects of the climate-change induced changes in weathering are not well studied and understood.

2-5.Author response:
We agree with the reviewer that normally we would expect changes in soil metal oxide contents (as well as soil texture and mineralogy) would happen over longer time periods, and there are not many warming studies that have investigated this topic, given the common belief that soil texture and mineralogy does not change within 10-20 years. However, this is a belief and not grounded in science, and we collated all literature and cited it showing that global change (land use, elevated CO2, warming) can change this at decadal scales. We were also surprised, but we show that this change happened. So this is not speculation, but grounded on robust data. We now wrote a separate paragraph, discussing the warming effects on soil metal oxides, soil texture and clay mineralogy. Due to the scarcity of other studies, we cited several examples of decadal changes of soil metal oxides, soil texture and mineralogy to soil management activities to strengthen the discussion. Besides, we will continue researching on this topic at our site in the future.

Manuscript:
So far, short-term (decadal) warming effects on soil metal oxides, soil texture and clay mineralogy have rarely been studied. The primary mineral is dolomite at our site. Goethite (iron hydroxide; α-FeO(OH)) constitutes the main phase of crystalline Fe in all soil samples at the Achenkirch site. We determined the content of crystalline iron and of amorphous iron in soils by wet chemistry (dithionite-and oxalate-extractable Fe). Oxalate-extractable represents the amorphous Fe oxyhydroxides (plus some humic-bound Fe) and dithionite-extractable minus oxalate-extractable Fe is the crystalline Fe. For the determination of soil mineralogy, we used X-ray diffraction (XRD), which only detects crystalline phases such as goethite, lepidocrocite, pyrite, hematite, etc. Ferrihydrite is mostly amorphous or very poorly crystallized. It is an Fe mineral, which can hardly be detected by XRD. Based on the results of Fe oxide contents, we get a range for the crystallised iron mineral (goethite) from 0.2 to 0.6 mass%, and a range for the amorphous iron (ferrihydrite) from 0.07 mass% to 0.19 mass%. These results also fit quite well to the results by XRD, where we found goethite in traces, which means <1 mass%.
Figures can be improved. Figure 1 can incorporate the complete variable name on PCA loadings. It is recommendable to use color blind friendly palettes (easy available in R). More elements for discussion could be derived from Figure 1, as the meanings or interpretation for PC1 or PC2.

2-7.Author response:
We updated our PCA figure with complete variable names and a color-blind friendly palette (the palette is from: http://jfly.iam.u-tokyo.ac.jp/color/; please see Figure 2 in the revised Display document).
On Thank you for your suggestion. We now use different symbols for warming (triangle) and control (circle) treatments in Figure 3. Besides, we made a schematic illustration (Figure 1), visualizing our results of long-term soil warming effects on soil P cycling (please see the revised Display document).
I encourage the authors to reinforce in a clearer way what is new from their contribution, and to remark its importance in relation to the global understanding of soil carbon and nutrient cycling.

2-9.Author response:
Thanks for the suggestion. We shortened the results summary and remarked the importance: 1) providing novel data of long-term warming effects on soil P process rates; 2) long-term warming can drive temperate forest soils to become P limited; 3) which can further affect soil C and N cycling.

Manuscript:
In conclusion, this study contributes novel data on warming effects on soil P processes, providing a more comprehensive understanding of climate change effects on the soil P cycle (Fig. 1). Our results suggest that long-term warming strongly reduced soil available P, which resulted from substantial losses of TP (via leaching and plant P uptake) and enhanced Pi sorption (onto Fe oxide and clay minerals), and can turn temperate forest soils to P limited (Du et al. We modified the sentence into "By the end of the century, global atmospheric temperatures are predicted to increase up to 5.7 °C above pre-industrial levels." (Lines 38-39).
Pag 5 line 100: Soil water loss is expected to be higher at the top soil than at the subsoil, is it like this? Can this relate to changes on DOP and DIP between different depths through a higher reduction of diffusion capacity on the top soil?

2-11. Author response:
This is an interesting notion, but we found similar responses of soil water content at both soil depths. Usually warming causes a soil drying effect, which, in this high precipitation area, is always reset after frequent rainfall. Topsoils and subsoils were therefore similarly affected. Moreover, according to the results of soil water content, 0-10 cm soil depths had higher soil water contents than the 10-20 cm layers (Table 1), which is likely due to a significantly lower soil sand content at 0-10 cm depth, implying potentially less soil water losses at 0-10 cm than at 10-20 cm depth. Besides, we modified the sentence to make this clearer (Line 115).
Pag 7 line 139: First time mention to elements of soil description, better mention them earlier.

2-12. Author response:
Thanks for the suggestion. As mentioned in 2-3, we moved this description to the site description section (in the Methods section; Lines 250-259) as this information fits better in that section. By doing so, if readers are interested in the soil formation and composition of our site, they can easily target where to find this information.
Pag 7 line 144: better "moderate" instead of high Pi sorption capacity when referring to kaolinite. It has lower sorption capacity than 2:1 clay. The same for line 175 when is mentioned "strong P-sorbing" kaolinite.
Pag 8 line 165: In relation with a previous comment asking for more information on mineralogy, are there proves of apatite precipitation on a general diffractogram?

2-14. Author response:
Thank you for this comment! Based on the XRD diffractograms, apatite was detectable in the Achenkirch soils, but only in small amounts being non-quantifiable. We revised the manuscript accordingly.

Manuscript:
The forest soils studied here have very high contents in exchangeable Ca 2+ and Mg 2+ , the cationexchange capacity being high, with a base saturation close to 100% (Table 1). Considering the near-neutral soil pH (Table 1), Ca 2+ could play a major role in Pi precipitation in the form of Caapatite, which is highly insoluble and therefore might act as another geochemical sink [Ca10(PO4)6(OH)2] (Tunesi et al., 1999). However, according to the X-ray diffractograms, the apatite content was very low at our site. Besides, long-term warming did not affect the exchangeable Ca 2+ pool (Table 2). Thus, the potential for Ca 2+ -P precipitation does not play a large role in both, the warming and control treatments, and it did not cause the higher abiotic P immobilization in the warming treatment (Fig. 2). Overall, this increased abiotic P immobilization in warmed soils mainly resulted from increased P sorption onto Fe oxyhydroxides and clays (dominated by moderate Psorbing kaolinite; Lines 169-180).
Pag, first paragraph: Could you discuss or compare the effect of inorganic P sorption vs. the increased root uptake when considering P limitation for the microbial pool? (a limitation that in turn may explain the microbial pool decrease under warming).

2-15. Author response:
We made two additional Pearson correlation figures (Fig. 3e and 3f) to show the relationships between microbial biomass P with total soil P and total Fe oxide content. Besides, we now briefly discuss how reduced total soil P and increased sorption onto Fe oxide potentially affect microbial P biomass pool.
Manuscript: This diminished P availability, due to decreased TP and increased P sorption, can further decrease microbial biomass P (MBP; According to the results of PCA and Pearson coefficient correlations, MBP is tightly and positively associated with total soil P, while it has weaker but significant negative relations with total Fe oxide (Fig. 2, 3e, and 3f), implying stronger effects on MBP limitations from TP losses than from increased sorption (onto Fe oxide; Lines 194-200). Methodology: Please specify why the sampling design was performed at 0-10 and 10-20 and how relates with soil horizons and composition.

2-16. Author response:
We added a new table (Table 1, please see in the revised Display document) showing the comparison of soil properties from these two soil depths in the warming and control treatments.
Please specify protocol or references for chloroform fumigation-extraction applied (line 287).

2-17. Author response:
Thanks for reminding us of this. We added the reference (Line 293 and Lines 584-585, reference 62).

Reviewer #3 (Remarks to the Author):
Major comments I think that the authors have responded to all the questions made by the two previous referees leaving clear all, but less the question of the increase of P leaching under warming, (see comments in the response letter) in my mind. I think that previous to the publication authors should allocate a further effort in leave clearer why and how warming increase leaching of P. We must take into account two circumstances that not should help to increase P leaching under warming. First the fact of that P is scarcely soluble, and second that warming increase P fixation in Fe oxides (by dropping pH) and plant P uptake thus taking off chance to increases P leaching. Thus, I believe that the authors should to provide a more consistent explanation of why warming increase the amounts of P leached out the soil. He seem to argue a higher root turn over leaving more P able to by leached, but the writing of this part is not very clear. In this sense some parts of the manuscripts make extrange this argument of more P losses by high root turn over and sounds partially contradictory: Lines 96-104: " ...reported an 128% increase in fine root production, 17% increase in fine root biomass, and unchanged fine root P content in the warming treatment compared to the control treatment. These results imply a higher P demand of the trees for fine root production and potentially greater root P uptake and P immobilization in long-lived plant biomass, ultimately reducing soil total P in warmed soils15,19,21. this substantially higher fine root production compared to moderate biomass increase indicate a faster fine root turnover, which suggests a reflux of P from decomposing root necromass into the soil, attenuating the soil P loss pathway from plant uptake." Lines 113-121 "Olsen Po in 10-20 cm (decrease from 1.16 in controls to 0.99 in warmed soils), indicating a higher net downward transport (leaching) of Olsen Po in warmed soils. Besides, even at high mean annual precipitation in old-growth forests, soil erosion and related particulate P losses likely do not play a large role, due to the high canopy and litter cover, effectively curtailing erosion in dense forests38. Overall, net losses of total P from the soils were mainly due to downward leaching of Olsen Po to lower soil layers, as the increased root P uptake was largely compensated by enhanced reflux of root P through increased root turnover. This is not sufficient clear are the authors claiming that in warming plots the higher P-Olsen leaching is due to the higher Phosphate release from dye roots by the higher root biomass with faster turnover, supposing that more Olsen-P is free in soil to be leached?.
But this argument is not full consistent given that first Phosphate has low solubility and moreover phosphate is also more uptaken by plants and fixed in Fe salts!. The authors can close better this part of the manuscript results, apart form this the manuscript is now suitable after a minor revision to be published in Nature Communications

Minor comments
Lines 29-30. "Warming decelerated the gross rates of phosphate mobilization by 21%, likely due to decreased soil total P pools (substrates)" What here means mobilization? Leaching? Release by mineralization?.
Line 219. "temperate forest soils to become P limited59" Moreover this is in the end Results/discussion paragraph that should be a synthesis of this study and the cite referring to other study provide some confusion. Thus I advise to make a concrete reference of the pass studies. For example "Thus warming reduced P-availability……………………….. in this study consistent with previous studies suggesting temperate forest soils under warming can become P limited59"

I advise a minor revision previous to publication
Tian et al. revised their manuscript following the comments of two reviewers. In the revised manuscript, they (i) extended the method descriptions, (ii) included a new figure and a new table, and (iii) rewrote parts of the manuscript. Altogether, the revision was done very thoroughly and most concerns of the reviewers were resolved. Yet, the introduction and hypotheses need to be improved and a broader perspective need to be implemented still. Because some of the findings challenge textbook knowledge, the authors must put more effort in eliminating alternative explanations.
Finally, some minor issues should be incorporated before the study can be published. In the following, the original reviewer comments are given in orange, the authors' response in green and my new comments in black.

Comments on author responses to reviewers
Reviewer #1: In its current format the manuscript fails to provide sufficient background to provide a rationale for the presented hypotheses Author response (shortened): We wrote a separate paragraph to explain why soil depth and seasonality are important in the context of this study.
New reviewer: There is still a mismatch between the background provided in the introduction and the hypotheses. On the one hand, neither soil depth nor seasonality (newly introduced) form part of the hypotheses. On the other hand, the expected directions of the warming effects ("promote", "increase", "decrease") are not backed up by explanations in the preceding introduction. For example, lines 49-54 do not explain responses of P cycling that are later stated as hypotheses. Therefore, the structure of the introduction and its match with the hypotheses need to be improved.
Reviewer #1: Lines 205-222: The conclusions paragraph is another example of the lack of depth here. The paragraph reads as a list of results and includes no references to other work.
Author response: We shortened the results and modified the conclusion. In a conclusion, however, it is not usual to cite (multiple) references, but rather to summarize the results and give an outlook on the implications of the work to be published. We therefore remarked the importance of this study: 1) providing novel data of long-term warming effects on soil P process rates; 2) long-term warming can drive temperate forest soils to become P limited; 3) which can further affect soil C and N cycling.
New reviewer: In addition to my comment on the phrasing (see below), I am still not convinced by the broader context of the conclusion. Why should we worry about soil (micro)organisms whose growth is potentially limited by P? And in which way would this be linked to soil C and N cyclingagain stressing the relevance of this link? Could P-limited soil (micro)organisms have an impact on the C sink function of the soil? Could P-limited soil (micro)organisms influence N losses (open N cycle if N is no longer limiting)? I strongly recommend that the authors spend some more thoughts on the broader implications of their study.
Reviewer #2: The authors argue possible biotic pathways to explain the decrease of total P pools. This includes a higher uptake by plants explained by an increase in fine root production. What are the implications and limitations of the experimental design to evaluate plant response to warming? In contrast to what happens with current climate change, in this case the soil is warmed but not the aboveground which restricts or unbalances plant response to belowground adaptations.
Author response: We agree with the reviewer that the results from soil warming experiment and soil+canopy warming experiment may differ, however, due to technical and financial constraints we are not aware of any warming experiment of a full mature temperate, boreal or tropical forest (above+belowground) with an average canopy height of >25 m. We would have ideas to do so, but this would also incur very strong unwanted micrometeorological effects and cost multi-millions of Euros to setup. With canopy warming, it most likely can increase gross plant P uptake from soil due to facilitated photosynthesis, but can also increase litter P inputs to soils. However, due to the relocation of foliar P from old leaves to other tissues, especially in P restricted environments, soil+canopy warming experiment may have higher net plant P uptake than soil warming experiment.
We are fully aware of that we only warmed limited part of trees in each plot. This was why we toned down the interpretation of plant P uptake pathway in our manuscript (Lines 102-105 and Lines 118-121).
New reviewer: I fully agree with the arguments of the authors. However, this constraint needs to be discussed briefly in the main text of the manuscript. If this explanation is missing, the reader will be tempted to infer implications e.g., on growth limitation of the forest by P and its consequences for the forest C sink, that must not be drawn based on the experimental design.
Reviewer #2: Higher Fe hydroxide content after warming treatments is attributed to faster weathering processes. This affirmation is surprising as a result of a 14-years warming. This is because weathering intensity directly relates to temperature, CO2 concentration and precipitation but it is generally attributed to longer time scales (millennial). There aren't many published studies considering the role of weathering changes at decadal time scales. I would appreciate that the authors develop more this idea including more references. At the moment the effects of the climatechange induced changes in weathering are not well studied and understood.
Author response: We agree with the reviewer that normally we would expect changes in soil metal oxide contents (as well as soil texture and mineralogy) would happen over longer time periods, and there are not many warming studies that have investigated this topic, given the common belief that soil texture and mineralogy does not change within 10-20 years. However, this is a belief and not grounded in science, and we collated all literature and cited it showing that global change (land use, elevated CO2, warming) can change this at decadal scales. We were also surprised, but we show that this change happened. So this is not speculation, but grounded on robust data. We now wrote a separate paragraph, discussing the warming effects on soil metal oxides, soil texture and clay mineralogy. Due to the scarcity of other studies, we cited several examples of decadal changes of soil metal oxides, soil texture and mineralogy to soil management activities to strengthen the discussion. Besides, we will continue researching on this topic at our site in the future.
New reviewer: With due respect, the time scales associated with weathering are no belief but itself also corroborated by data (see body of literature on changes in soil properties in chronosequence studies). Nevertheless, I am in favor of challenging the long-term perspective of weathering. However, this can only be achieved by thoroughly eliminating alternative explanations for your findings. One such explanation is an a priori difference between the pairs of plots. For example, the high heterogeneity within the control and warming treatments (e.g. l. 238-239) increases the risk of initially selecting control and warming plots differing in soil properties -just by chance. These concerns can be dispelled by data on soil properties of the plots at the time of the experimental set up i.e., before the start of the warming treatment. Are data on initial soil properties such as soil texture and mineralogy available? Or do archived soil samples exist that could be analyzed still? How do these data relate to your findings 14 years later? Without data on initial soil properties, the causality of the warming effects on soil texture and mineralogy remains questionable and all corresponding statements need to be toned down. 118-121 Statements too strong because you did neither determine DOP leaching nor root P uptake/reflux, please tone down. "net losses of total P from the soils seem to be mainly due to" and "as the increased root P uptake likely was largely compensated".
173-174 Where are these results shown/specified? 177 Statement too strong, please rephrase ("it cannot explain the higher abiotic P immobilization").
189 "stronger stimulation" (because "than" follows in the second part of the sentence)    We thank the reviewers for their careful reading and constructive comments, which greatly helped us to further improve our manuscript! We addressed each comment individually. Given that the new reviewer #4 commented on the former comments of reviewer #1 and #2 and our responses, we adopted the coloring scheme. The comments of the former reviewers #1 and #2 are in Orange/Red, our previous responses to reviewers #1 and #2 in Green. The comments by the new reviewers #3 and #4 are in Black, our responses to reviewers #3 and #4 are in Blue and our changes in the revised manuscript are highlighted in yellow and indexed with the line numbers in the revised manuscript. Besides, to make the story coherent and smooth, we did minor revisions in the sections, "Warming effects on abiotic P processes" and "Warming effects on biotic P processes", and highlighted these changes in Green in the revised manuscript.

Reviewer #3 (Remarks to the Author):
Major comments I think that the authors have responded to all the questions made by the two previous referees leaving clear all, but less the question of the increase of P leaching under warming, (see comments in the response letter) in my mind. I think that previous to the publication authors should allocate a further effort in leave clearer why and how warming increase leaching of P. We must take into account two circumstances that not should help to increase P leaching under warming. First the fact of that P is scarcely soluble, and second that warming increase P fixation in Fe oxides (by dropping pH) and plant P uptake thus taking off chance to increases P leaching. Thus, I believe that the authors should to provide a more consistent explanation of why warming increase the amounts of P leached out the soil. He seems to argue a higher root turn over leaving more P able to by leached, but the writing of this part is not very clear. In this sense some parts of the manuscripts make extrange this argument of more P losses by high root turn over and sounds partially contradictory: Lines 96-104: " ...reported an 128% increase in fine root production, 17% increase in fine root biomass, and unchanged fine root P content in the warming treatment compared to the control treatment. These results imply a higher P demand of the trees for fine root production and potentially greater root P uptake and P immobilization in long-lived plant biomass, ultimately reducing soil total P in warmed soils15,19,21. this substantially higher fine root production compared to moderate biomass increase indicate a faster fine root turnover, which suggests a reflux of P from decomposing root necromass into the soil, attenuating the soil P loss pathway from plant uptake." Lines 113-121 "Olsen Po in 10-20 cm (decrease from 1.16 in controls to 0.99 in warmed soils), indicating a higher net downward transport (leaching) of Olsen Po in warmed soils. Besides, even at high mean annual precipitation in old-growth forests, soil erosion and related particulate P losses likely do not play a large role, due to the high canopy and litter cover, effectively curtailing erosion in dense forests38. Overall, net losses of total P from the soils were mainly due to downward leaching of Olsen Po to lower soil layers, as the increased root P uptake was largely compensated by enhanced reflux of root P through increased root turnover.
This is not sufficient clear are the authors claiming that in warming plots the higher P-Olsen leaching is due to the higher Phosphate release from dye roots by the higher root biomass with faster turn-over, supposing that more Olsen-P is free in soil to be leached?.
But this argument is not full consistent given that first Phosphate has low solubility and moreover phosphate is also more uptaken by plants and fixed in Fe salts!. The authors can close better this part of the manuscript results, apart from this the manuscript is now suitable after a minor revision to be published in Nature Communications

3-1. Author response:
Thank you for this comment! We re-evaluated different potential pathways for soil P losses, i.e., plant P uptake, downward P transportation (both dissolved and particulate P), atmospheric P losses, and P losses via soil erosion/runoff. We re-wrote the section, "Warming effects on soil P pools and P losses", discussing the potential contributions of each pathway in our revised manuscript.
Instead of considering dissolved organic P leaching as the main reason for the total soil P losses, we here more specifically expand on other factors already mentioned in the previous manuscript version, i.e., (1) plant P uptake (experimental setup induced net P transfer from soil to plant) and (2) downward P transportation (especially particulate P through preferential flow paths) as the main reasons for total soil P losses at our site, whereas P losses to the atmosphere and through soil erosion (likely) played minor roles (for a detailed description, please read the revised manuscript below and in lines 90-150). Besides, we accordingly updated Fig.1, the schematic illustration, and linked with the section, "Warming effects on abiotic processes" in lines 211-215.

Revised manuscript:
After 14 years of warming, we found substantial losses of total soil P (TP) from the 0-10 cm (-18%) and the 10-20 cm (-30%) soil layer in the warming treatment compared to the control treatment (Tables 1 and 2). There are different pathways potentially causing soil TP losses, i.e., plant P uptake, downward transportation of particulate and dissolved P, atmospheric P losses, and P losses through soil erosion/runoff (Fig. 1).
Elevated temperatures, in general, facilitate plant growth while warming had no effects on plant C:P ratios in temperate forest ecosystems Lu et al., 2013). Greater biomass production indicates higher plant P uptake, which removes P from soil and allocates this to the plant compartment, in turn reducing the total soil P pools. Kengdo et al., (2022) who studied fine root production, morphology, and element contents at the same site, reported a 128% increase in fine root production and a 17% increase in fine root biomass, but unaltered fine root P concentrations in the warming treatment compared to the control treatment. These results imply a higher P demand of the trees for fine root production, but they do not account for potentially greater plant P immobilization in aboveground tissues (Lie et al., 2022). The potentially larger aboveground P stock should eventually return to the soils, which might (partially) compensate the soil P losses by fine root uptake and aboveground P allocation in the warming treatment (Sohrt et al., 2017). However, due to the small plot size (2 by 2 meters) and soil-only warming (without canopy warming), the roots and canopies of trees are shared across the warming and the control treatments, and across experimental and non-experimental areas, causing comparable litterfall P returns in warmed and un-warmed areas. Therefore, increased gross plant P uptake in the warming treatment combined with comparable plant litter P returns between treatments will result in the redistribution of P, ultimately reducing soil TP in warmed soils in the long run.
Soil P can also be lost from terrestrial systems as dissolved P and P that is bound to soil particles (e.g. colloidassociated P and particulate P) through subsurface flux ( . This may not only increase dissolved P losses, but also colloidal and particulate ones due to sorption of Pi to colloidal and nano-particulate clays and metal oxyhydroxides, the latter of which significantly increased in warmed soils.
Direct soil P losses to the atmosphere are negligible, with phosphine being the only gaseous P form. Phosphine is highly reduced and reactive, being rapidly oxidized to non-gaseous forms of P under aerobic conditions, hence explaining the very low gaseous P emissions from soils (

Minor comments
Lines 29-30. "Warming decelerated the gross rates of phosphate mobilization by 21%, likely due to decreased soil total P pools (substrates)" What here means mobilization? Leaching? Release by mineralization?.

3-2. Author response:
Thanks for pointing this out! The gross rates of phosphate mobilization include both biotic (microbial) and abiotic phosphate mobilization (release), i.e., organic P mineralization, and P desorption and dissolution. We now added this information to the revised manuscript, "Warming decelerated the gross rates of phosphate mobilization (including microbial P mineralization, and P desorption and dissolution) by 21%,…" (lines 33-34).
Line 219. "temperate forest soils to become P limited59" Moreover this is in the end Results/discussion paragraph that should be a synthesis of this study and the cite referring to other study provide some confusion. Thus I advise to make a concrete reference of the pass studies. For example "Thus warming reduced P-availability……………………….. in this study consistent with previous studies suggesting temperate forest soils under warming can become P limited59"

3-3. Author response:
We deleted the reference. Besides, combined with comment 4-19, we revised this sentence to "and can turn the soil microbes in temperate forest soils to become P limited." (line 255-256).
I advise a minor revision previous to publication

Reviewer #4 (Remarks to the Author):
Tian et al. revised their manuscript following the comments of two reviewers. In the revised manuscript, they (i) extended the method descriptions, (ii) included a new figure and a new table, and (iii) rewrote parts of the manuscript. Altogether, the revision was done very thoroughly and most concerns of the reviewers were resolved. Yet, the introduction and hypotheses need to be improved and a broader perspective need to be implemented still. Because some of the findings challenge textbook knowledge, the authors must put more effort in eliminating alternative explanations. Finally, some minor issues should be incorporated before the study can be published. In the following, the original reviewer comments are given in orange, the authors' response in green and my new comments in black.

Comments on author responses to reviewers
Reviewer #1: In its current format the manuscript fails to provide sufficient background to provide a rationale for the presented hypotheses Author response (shortened): We wrote a separate paragraph to explain why soil depth and seasonality are important in the context of this study.
New reviewer: There is still a mismatch between the background provided in the introduction and the hypotheses. On the one hand, neither soil depth nor seasonality (newly introduced) form part of the hypotheses. On the other hand, the expected directions of the warming effects ("promote", "increase", "decrease") are not backed up by explanations in the preceding introduction. For example, lines 49-54 do not explain responses of P cycling that are later stated as hypotheses. Therefore, the structure of the introduction and its match with the hypotheses need to be improved.

4-1. Author response:
Thanks for the comment! We revised the introduction, more tightly linking the hypotheses with the preceding introduction (lines 56-67 and 83-89). Regarding soil depth and seasonality, the main focus of this study is long-term soil warming effects on soil P cycling. The reason for including soil depth and seasonality in this study was to provide a more thorough understanding of these warming effects across soil depths and seasons, i.e., to show whether warming effects are consistent across seasons and soil depths or whether they are more context-dependent. Thus, we prefer to keep the story focused and only address the potential interactive soil depth and seasonality effects in the introduction (lines 73-79) and in the discussion (lines 256-259). Formulating hypotheses for seasonal and soil depth effects would also generally be hard, given the lack of literature on such effects on P cycling under warming scenarios.

Revised manuscript:
Soil P cycling is driven by biotic and abiotic processes. Some studies have analyzed the biotic side by investigating warming effects on soil phosphatase activities and on soil P mobilization ( Hypotheses: long-term warming will (i) promote biological soil P processes, i.e., phosphomonoesterase activity due to the lack of drought offsets of the warming effect, (ii) hinder P sorption relative to desorption, and (iii) thereby increase gross rates of soil P mobilization through biotic and abiotic processes. The increase in soil P mobilization will be reflected in increased microbial (and fine root) P uptake, but will increase the risk of soil P losses at the same time. Author response: We shortened the results and modified the conclusion. In a conclusion, however, it is not usual to cite (multiple) references, but rather to summarize the results and give an outlook on the implications of the work to be published. We therefore remarked the importance of this study: 1) providing novel data of long-term warming effects on soil P process rates; 2) long-term warming can drive temperate forest soils to become P limited; 3) which can further affect soil C and N cycling.
New reviewer: In addition to my comment on the phrasing (see below), I am still not convinced by the broader context of the conclusion. Why should we worry about soil (micro)organisms whose growth is potentially limited by P? And in which way would this be linked to soil C and N cycling -again stressing the relevance of this link? Could P-limited soil (micro)organisms have an impact on the C sink function of the soil? Could P-limited soil (micro)organisms influence N losses (open N cycle if N is no longer limiting)? I strongly recommend that the authors spend some more thoughts on the broader implications of their study.

4-2. Author response:
We revised conclusion and now specified how microbial P limitation would potentially affect ecosystem C and N cycling (lines 250-274).

Revised manuscript:
In conclusion, this study contributes novel data on warming effects on soil P processes, providing a more comprehensive understanding of climate change effects on the complex soil P cycle (Fig. 1). Our results suggest that long-term warming reduced bioavailable P, which resulted from substantial losses of TP (likely via plant P uptake and downward P transportation) and increased Pi sorption (onto Fe oxyhydroxides and clay minerals), and can turn the soil microbes in temperate forest soils to become P limited. Moreover, according to the results of the mixed-effects models, most of the measured P pools and processes showed no interactions between warming and soil depth and/or season ( , we therefore expect that the intensified competition between plants and soil microbes for this scarce resource will have negative consequences for plant net primary production and ecosystem C sequestration with climate warming. We however note that extrapolations of the soil warming effects found here to the ecosystem level needs to be done cautiously, given that we only warmed soils, and here only parts of a trees' root system, but not the aboveground compartment. Whole ecosystem warming might even further impair the delicate balance between P limited trees and soil microbes, given that warming increases the plant P demand.
Reviewer #2: The authors argue possible biotic pathways to explain the decrease of total P pools. This includes a higher uptake by plants explained by an increase in fine root production. What are the implications and limitations of the experimental design to evaluate plant response to warming? In contrast to what happens with current climate change, in this case the soil is warmed but not the aboveground which restricts or unbalances plant response to belowground adaptations.
Author response: We agree with the reviewer that the results from soil warming experiment and soil+canopy warming experiment may differ, however, due to technical and financial constraints we are not aware of any warming experiment of a full mature temperate, boreal or tropical forest (above+belowground) with an average canopy height of >25 m. We would have ideas to do so, but this would also incur very strong unwanted micrometeorological effects and cost multi-millions of Euros to setup. With canopy warming, it most likely can increase gross plant P uptake from soil due to facilitated photosynthesis, but can also increase litter P inputs to soils. However, due to the relocation of foliar P from old leaves to other tissues, especially in P restricted environments, soil+canopy warming experiment may have higher net plant P uptake than soil warming experiment. We are fully aware of that we only warmed limited part of trees in each plot. This was why we toned down the interpretation of plant P uptake pathway in our manuscript (Lines 102-105 and Lines 118121).
New reviewer: I fully agree with the arguments of the authors. However, this constraint needs to be discussed briefly in the main text of the manuscript. If this explanation is missing, the reader will be tempted to infer implications e.g., on growth limitation of the forest by P and its consequences for the forest C sink, that must not be drawn based on the experimental design.

4-3. Author response:
We now addressed that our experiment is based on soil warming (without canopy warming) in the manuscript. We amended the text in the Discussion "However, due to the small plot size (2 by 2 meters) and soil-only warming (without canopy warming), the roots and canopies of trees are shared across the warming and the control treatments, and across experimental and non-experimental areas, causing comparable litterfall P returns in warmed and un-warmed areas. Therefore, increased gross plant P uptake in the warming treatment combined with comparable plant litter P returns between treatments will result in the redistribution of P, ultimately reducing soil TP in warmed soils in the long run." (lines 107-114) To make this point clearer we further added in the Conclusions that: "We however note that extrapolations of the soil warming effects found here to the ecosystem level needs to be done cautiously, given that we only warmed soils, and here only parts of a trees' root system, but not the aboveground compartment. Whole ecosystem warming might even further impair the delicate balance between P limited trees and soil microbes, given that warming increases the plant P demand." (lines 269-274) Reviewer #2: Higher Fe hydroxide content after warming treatments is attributed to faster weathering processes. This affirmation is surprising as a result of a 14-years warming. This is because weathering intensity directly relates to temperature, CO2 concentration and precipitation but it is generally attributed to longer time scales (millennial). There aren't many published studies considering the role of weathering changes at decadal time scales. I would appreciate that the authors develop more this idea including more references. At the moment the effects of the climate change induced changes in weathering are not well studied and understood.
Author response: We agree with the reviewer that normally we would expect changes in soil metal oxide contents (as well as soil texture and mineralogy) would happen over longer time periods, and there are not many warming studies that have investigated this topic, given the common belief that soil texture and mineralogy does not change within 10-20 years. However, this is a belief and not grounded in science, and we collated all literature and cited it showing that global change (land use, elevated CO2, warming) can change this at decadal scales. We were also surprised, but we show that this change happened. So this is not speculation, but grounded on robust data. We now wrote a separate paragraph, discussing the warming effects on soil metal oxides, soil texture and clay mineralogy. Due to the scarcity of other studies, we cited several examples of decadal changes of soil metal oxides, soil texture and mineralogy to soil management activities to strengthen the discussion. Besides, we will continue researching on this topic at our site in the future.
New reviewer: With due respect, the time scales associated with weathering are no belief but itself also corroborated by data (see body of literature on changes in soil properties in chronosequence studies). Nevertheless, I am in favor of challenging the long-term perspective of weathering. However, this can only be achieved by thoroughly eliminating alternative explanations for your findings. One such explanation is an a priori difference between the pairs of plots. For example, the high heterogeneity within the control and warming treatments (e.g. l. 238-239) increases the risk of initially selecting control and warming plots differing in soil properties -just by chance. These concerns can be dispelled by data on soil properties of the plots at the time of the experimental set up i.e., before the start of the warming treatment. Are data on initial soil properties such as soil texture and mineralogy available? Or do archived soil samples exist that could be analyzed still? How do these data relate to your findings 14 years later? Without data on initial soil properties, the causality of the warming effects on soil texture and mineralogy remains questionable and all corresponding statements need to be toned down.

4-4. Author response:
Thanks for pointing this out. You are right and we therefore ask to apologize for overdoing our response. The experimental set-up meant that across the site at six locations paired plots were established directly aside of each other, both manipulated by burying heating cables, but only one set functional (heated) and the other unfunctional (control). This block design controls for much of the spatial heterogeneity one finds in mountain forests. During data analysis, we took the block effects into consideration and thus we set block as random factor in the mixed effects models. Unfortunately, we do not have historical data of the original soil conditions, neither do we have archived soils to compared historical plot data to those measured now. Therefore, we toned down the corresponding statements (lines 188-198).
Figure 1: You did not measure plant P (= either above-or belowground P stocks or both). Stick to those variables for which results are presented in this manuscript.

4-25. Author response:
The aim of this schematic illustration is to visualize the P flows at our site. Since plant P uptake is an important pathway explaining soil P losses and of plant responses to P limitations, we would still like to keep it in the schematic illustration. We now added the reference number next to plant P uptake in the figure and explained in the caption that these results are retrieved from Kengdo et al., 2022, who studied fine root production and element content at the same site in the same year.

4-26. Author response:
Thank you for the suggestion. Since dithionite extracted Fe includes both crystalline and amorphous Fe oxyhydroxides, we decided to keep sub-figures a+b and remove sub-figures c+d (for the updated figure, please see the revised display document).
The manuscript "Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses" by Tian et al. take profit of a long time manipulation of warming in Alpine forests to study the long term impacts on soil P status. The experiment is correct; consist in a block design with six blocks with a control and warming treatment.
The study must be considered seriously to be published by the solidity of the experimental design, the longtime run of the warming treatment and overall of the lack of knowledge of warming impact of "in situ" P status. I have observed that the current version is the result as a first revision; after reading detailed the manuscript without doubt, the manuscript needs many improvements/corrections/clarifications to clearly state and identify the take home lessons that it has. Thus, my advice is to return the manuscript to the authors to improve it previously to its publication. See my detailed comments. Abstract in general, the overall results allows to make a general picture of the results, something like " Warming increased the sorption to more recalcitrant soil P fractions (absorbed in oxyhydroxydes and clays), and higher outputs of P from soils by increasing plant P uptake and vertical fluxes of colloidal and particulate P contributing all them to the drop of available and labile soil P fractions in warmed soils. Despite microbes increased acid phosphatase activity this was not sufficient to avoid a decrease of available and labile soil P forms." Take note that the title ends with "…phosphorus losses" thus this question should be clearly stated also in the abstract. 4.Line 51 ".., showing overall increases in plant N:P ratios" Please add some bibliography support to sustain this part of the sentence. 5 Have authors some further result sustaining the soil pores changes favoring (or potentially favoring) the seepage of P? 11.Lines 142-145. Phosphines are negligible in nature , several reports conclude it I advise to take out this from thhe manuscript. 12.Lines 147-150. I suggest to clearly stated this sentence to provide a clerar take home lesson of the concrete results of the current study, I suggest: "In our experiment the results strongly suggest that the main causes of total soil P losses unde warming are due to an increase of plant P-uptake and subsurface dissolved and colloidal/particulate P fluxes. 13.Lines 156-157 Cahnge to more clear: "This formation of more recalcitramt P stocks could have taken place via sorption (on to….., forming Ca-apatite (Fig. 1)." 14. Lines 176-177. Please take into account that Kaolinites are 1:1 clays with a low capacity to absorb. 15. Lines 185-187. Yes more clay and less sand should increase at some extend the capacity to absorp P in this case increase it, but moreover also should make more difficult the P infiltration, counteracting the effect of more porosity by higher root turn-over. This together with the fact that if we argue that plants taken up more P this should be accompanied by more growth and water up-take under warming decreasing the potential of nutrient soil mobilization by infiltration. This is the main not clear/resolved variable, that should be specifically clarified by authors, putting altogether the variables that can play in the increase or decrease of P infiltration and loss from the studied upper parts of soil. 20.In general in the last conclusions paragraph. State clearly if plants growth more under warming, in this case warming allows plant to accumulate sources and take profit in production capacity with a net transfer of P from soil to plant, being the microbes the lossers in the competition plant-microbes under warming, a very important question that should be clarified here.
21.Line 296. The authors should check the use of concentrations and contents throughout the manuscript.
Reviewer #4 (Remarks to the Author): Tian et al. revised their manuscript a second time following the comments of two reviewers. In the revised manuscript, they streamlined the introduction and discussion, they embedded their study in a broader context and they implemented all other changes requested by the reviewers. I would like to congratulate the authors for their careful and comprehensive second revision. There is only one tiny issue left that has not been fully addressed. Without repeating reviewer comments and author responses, I would like to draw the attention to the mentioning of soil depth and seasonality in the introduction (lines 73-79). I agree with the authors that the story should be kept focused and soil depth/seasonality should not be included in the hypotheses. Following this reasoning, these two aspects do not need to be explained in the introduction where they raise misleading expectations. Therefore, I recommend to delete this paragraph in the introduction and just use it to highlight the robustness of the findings in the discussion.
We thank the reviewers for their comments, which helped us improve the manuscript. We addressed each comment individually. The responses are in green for clarity, and corresponding changes are highlighted in yellow in the revised manuscript.

REVIEWERS' COMMENTS
Reviewer #3 (Remarks to the Author): The manuscript "Long-term soil warming decreases microbial phosphorus utilization by increasing abiotic phosphorus sorption and phosphorus losses" by Tian et al. take profit of a long time manipulation of warming in Alpine forests to study the long term impacts on soil P status. The experiment is correct; consist in a block design with six blocks with a control and warming treatment. The study must be considered seriously to be published by the solidity of the experimental design, the longtime run of the warming treatment and overall of the lack of knowledge of warming impact of "in situ" P status. I have observed that the current version is the result as a first revision; after reading detailed the manuscript without doubt, the manuscript needs many improvements/corrections/clarifications to clearly state and identify the take home lessons that it has. Thus, my advice is to return the manuscript to the authors to improve it previously to its publication. See my detailed comments.
Comments for Authors 1.I advise to move the sentence of lines 35-36 before the sentence in lines 33-35.

3-1. Author Response:
Combined with the next two comments, we revised our Abstract as follow, "Phosphorus (P) is an essential and often limiting element that could play a crucial role in terrestrial ecosystem responses to climate warming. However, it has yet remained unclear how different P cycling processes are affected by warming. Here we investigated the response of soil P pools and P cycling processes in a mountain forest after 14 years of soil warming (+4°C). Long-term warming decreased soil total P pools, likely due to higher outputs of P from soils by increasing net plant P uptake and downward transportation of colloidal and particulate P. Warming increased the sorption strength to more recalcitrant soil P fractions (absorbed to iron oxyhydroxides and clays), thereby further reducing bioavailable P in soil solution. As a response, soil microbes enhanced the production of acid phosphatase, though this was not sufficient to avoid decreases of soil bioavailable P and microbial biomass P (and biotic phosphate immobilization). This study therefore highlights how long-term soil warming triggers changes in biotic and abiotic soil P pools and processes, which can potentially aggravate the P constraints of the trees and soil microbes and thereby negatively affect the C sequestration potential of these forests." (Lines 28-42) 2.Lines 38-39 "…, though this did not…….microbial biomass P" what exactly this means, what have exactly of different microbial biomass P from biotic P, immobilization, at least both overlap!!!

3-2. Author Response:
Indeed, biotic P immobilization (here the process of microbial 33 Pi uptake) and microbial biomass P (a soil P pool, not a process, driven by the balance of P uptake, storage and turnover/death, but certainly larger biomass also triggers greater microbial P uptake) are two parameters that are or can be highly connected. Since we measured both parameters with different methods, we meant to present both results, which are consistent with each other. Please see the revision in response 3-1.
3.Abstract in general, the overall results allows to make a general picture of the results, something like " Warming increased the sorption to more recalcitrant soil P fractions (absorbed in oxyhydroxydes and clays), and higher outputs of P from soils by increasing plant P uptake and vertical fluxes of colloidal and particulate P contributing all them to the drop of available and labile soil P fractions in warmed soils. Despite microbes increased acid phosphatase activity this was not sufficient to avoid a decrease of available and labile soil P forms." Take note that the title ends with "…phosphorus losses" thus this question should be clearly stated also in the abstract.
Tian et al. revised their manuscript a second time following the comments of two reviewers. In the revised manuscript, they streamlined the introduction and discussion, they embedded their study in a broader context and they implemented all other changes requested by the reviewers. I would like to congratulate the authors for their careful and comprehensive second revision. There is only one tiny issue left that has not been fully addressed. Without repeating reviewer comments and author responses, I would like to draw the attention to the mentioning of soil depth and seasonality in the introduction (lines 73-79). I agree with the authors that the story should be kept focused and soil depth/seasonality should not be included in the hypotheses. Following this reasoning, these two aspects do not need to be explained in the introduction where they raise misleading expectations. Therefore, I recommend to delete this paragraph in the introduction and just use it to highlight the robustness of the findings in the discussion.

4-1. Author Response:
Thank you for your positive feedback!
Regarding the comment, we deleted the paragraph, which introduces soil depth and seasonality, and added one sentence, "Moreover, the expected warming effects on P pools and cycling processes were tested across soil depth and season to evaluate their consistency or their context dependence.", to briefly address our experimental setup in lines 85-87.